In a June 2018 article published in the Journal of Animal Science, researchers investigated the relationship between feed efficiency (FE) in pigs and their cecal mucosal microbiota. Their intent was to better understand how microbial and host factors might potentially affect FE in pigs.

Gut microbes can potentially influence nutrient digestion and energy utilization of their hosts, which has important implications in animal food production. However, there is considerable difficulty in characterizing causal links between FE and gut microbes due to the varied complex interactions between host, microbes, and environment. Therefore, the authors emphasize a need to better study these areas in order to fill gaps in the current scientific knowledge.

In this study, 72 Austrian pigs were evaluated for RFI. Pigs were raised under the same environmental and feed conditions, weaned at 28 days, and selected based on RFI extremes. Eight pigs were identified as low residual feed intake (LRFI) and eight were identified as high residual feed intake (HRFI). The study period lasted from day 42 to 91. Cecal digesta and mucosa were collected and analyzed with Illumina 16S MiSeq. The authors hypothesized there would be differences in cecal microbiota and gene expression with extremes in RFI.

The RFI was 2.1 kg less in LRFI pigs. Body weight at slaughter of LRFI and HRFI pigs was not statistically different (106 versus 110 kg, respectively), although the LRFI pigs consumed 360 g/day less food. The ADFI and ADG were comparable. Analysis of cecal microbiota indicated no significant difference in microbial absolute abundance or microbial diversity, and phylum-level populations were similar. However, significant differences were noted at the species-level. In LRFI pigs, Campylobacter species were significantly more abundant, while Escherichia, Shigella, Ruminobacter, and Veillonella species were significantly less abundant. There was also increased expression of genes associated with signaling and uptake of volatile fatty acids (VFA), and decreased expression of genes associated with gut barrier integrity (MUC2, ZON1) in LRFI pigs. Interestingly, there was no difference in VFA or microbial lipopolysaccharide concentration in cecal digesta of the LRFI and HRFI pigs studied.

The authors’ hypothesis was supported by their data, as there were significant differences in cecal bacteria at the species-level and host gene expression in LRFI versus HRFI pigs. However, due to the complex and varied multiple factors that can influence the cecal microbiota, these results only suggest an association between FE, host gene expression, and cecal microbes. The authors also stress that it cannot be determined if these noted differences were the cause of, or the result of, differences in RFI. This study also suggests a need to better understand the finding of increased Campylobacter in LRFI pigs, as this species is a known pathobiont. Overall, the interactions between host-microbe and host gene expression as it relates to FE in pigs warrants more research into the functional profiles of cecal microbiota using a systems approach.

To view the full article, “Interactions between metabolically active bacteria and host gene expression at the cecal mucosa in pigs of diverging feed efficiency,” visit Journal of Animal Science.